<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
    <title>Three.js - Canvas Textured Cube</title>
    <style>
    html, body {
        height: 100%;
        margin: 0;
    }
    #c {
        width: 100%;
        height: 100%;
        display: block;
    }
    </style>
  </head>
  <body>
    <canvas id="c"></canvas>
  </body>
<script type="importmap">
{
  "imports": {
    "three": "../../build/three.module.js"
  }
}
</script>

<script type="module">
import * as THREE from 'three';

function main() {

	const canvas = document.querySelector( '#c' );
	const renderer = new THREE.WebGLRenderer( { antialias: true, canvas } );

	const fov = 75;
	const aspect = 2; // the canvas default
	const near = 0.1;
	const far = 5;
	const camera = new THREE.PerspectiveCamera( fov, aspect, near, far );
	camera.position.z = 2;

	const scene = new THREE.Scene();

	const boxWidth = 1;
	const boxHeight = 1;
	const boxDepth = 1;
	const geometry = new THREE.BoxGeometry( boxWidth, boxHeight, boxDepth );

	const cubes = []; // just an array we can use to rotate the cubes
	const ctx = document.createElement( 'canvas' ).getContext( '2d' );
	ctx.canvas.width = 256;
	ctx.canvas.height = 256;
	ctx.fillStyle = '#FFF';
	ctx.fillRect( 0, 0, ctx.canvas.width, ctx.canvas.height );
	const texture = new THREE.CanvasTexture( ctx.canvas );

	const material = new THREE.MeshBasicMaterial( {
		map: texture,
	} );
	const cube = new THREE.Mesh( geometry, material );
	scene.add( cube );
	cubes.push( cube ); // add to our list of cubes to rotate

	function resizeRendererToDisplaySize( renderer ) {

		const canvas = renderer.domElement;
		const width = canvas.clientWidth;
		const height = canvas.clientHeight;
		const needResize = canvas.width !== width || canvas.height !== height;
		if ( needResize ) {

			renderer.setSize( width, height, false );

		}

		return needResize;

	}

	function rand( min, max ) {

		if ( max === undefined ) {

			max = min;
			min = 0;

		}

		return Math.random() * ( max - min ) + min;

	}

	function randVelocity() {

		return rand( 2, 4 ) * ( rand( 2 ) < 1 ? - 1 : 1 );

	}

	const maxLines = 60;
	const points = [
		{ position: [ rand( 256 ), rand( 256 ) ], direction: [ randVelocity(), randVelocity() ] },
		{ position: [ rand( 256 ), rand( 256 ) ], direction: [ randVelocity(), randVelocity() ] },
	];
	const lineHistory = [];
	let lineCursor = 0;

	function drawCurrentLine() {

		const line = lineHistory[ lineCursor ];
		ctx.beginPath();
		ctx.moveTo( ...line[ 0 ] );
		ctx.lineTo( ...line[ 1 ] );
		ctx.stroke();

	}

	function drawLines( time ) {

		points.forEach( ( point ) => {

			point.position.forEach( ( position, ndx ) => {

				const newPosition = position + point.direction[ ndx ];
				if ( newPosition > 255 ) {

					point.direction[ ndx ] = rand( - 2, - 4 );

				} else if ( newPosition < 0 ) {

					point.direction[ ndx ] = rand( 2, 4 );

				}

				point.position[ ndx ] = newPosition;

			} );

		} );
		if ( lineHistory.length === maxLines ) {

			ctx.lineWidth = 3;
			ctx.strokeStyle = '#FFF';
			drawCurrentLine();

		}

		lineHistory[ lineCursor ] = points.map( point => point.position.slice() );
		ctx.lineWidth = 1;
		ctx.strokeStyle = hsl( time, 1, .5 );
		drawCurrentLine();
		lineCursor = ( lineCursor + 1 ) % maxLines;

	}

	function hsl( h, s, l ) {

		return `hsl(${h * 360 | 0},${s * 100 | 0}%,${l * 100 | 0}%)`;

	}

	function render( time ) {

		time *= 0.001;

		if ( resizeRendererToDisplaySize( renderer ) ) {

			const canvas = renderer.domElement;
			camera.aspect = canvas.clientWidth / canvas.clientHeight;
			camera.updateProjectionMatrix();

		}

		drawLines( time * 0.1 );
		texture.needsUpdate = true;

		cubes.forEach( ( cube, ndx ) => {

			const speed = .2 + ndx * .1;
			const rot = time * speed;
			cube.rotation.x = rot;
			cube.rotation.y = rot;

		} );

		renderer.render( scene, camera );

		requestAnimationFrame( render );

	}

	requestAnimationFrame( render );

}

main();
</script>
</html>
